1. Technical Field
The present invention relates to battery charge, and more particularly to a method of charging a battery by adaptively applying an optimized charging pattern for each of the battery phases using an entropy profile of the battery that is thermodynamic information of the battery.
2. Description of the Related Art
Today, around 1.3 billion people have no access to electricity and this number is currently projected to barely change in the foreseeable future. It is forecasted that some 1.2 billion people globally will be still situated in an environment without access to electricity in 2030. The problem is particularly acute in rapidly developing areas of Asia and Africa, where the combination of population growth and industrial development is placing huge demands on the existing electrical infrastructure. However, in the countries where the distribution grid infrastructure itself is lacking, another market for domestic and consumer applications which are not connected to mains electricity is growing rapidly. Devices from the market are frequently powered by batteries, kerosene or diesel generators. However, as the fossil energy will disappear in the near future and new actors such as China or India are absorbing all the oil and gas production increase, it is predicted that the need for batteries will grow significantly over the next decades.
There are also increasing demands for off-grid applications in the developed countries. The people in the countries are using more and more portable electronics such as laptop computers, smartphones, and the like. Markets of electrical vehicles (EV) or hybrid electric vehicles (HEV) start to stretch themselves as the people embrace them due to concerns about environment and economy. In these countries, the internet of things (IoT) is also rapidly increasing, in addition to the already growing demand for energy storage solutions.
The main solution to store electricity in all these devices is the battery even if sometimes small systems rely on hyper-capacitors as well. The majority of currently used batteries are lithium-based batteries such as Li-Ion, Life-Po, etc. due to their higher power densities and fast charging abilities. Also, the lithium-based batteries have low self-discharge, and don't have any requirements for priming. Thus, nowadays the lithium-based batteries are used to power a wide variety of consumer goods ranging from the mobile phones to children toys, e-bikes and passenger vehicles. The lithium-based batteries are already the majority of the battery market, and demands for them are still increasing continuously, with an expectation of their markets to grow 4 times by 2020.
Recently, a hyper capacitor is emerging as a new way to store energy. The hyper capacity provides a high energy density and thus can store almost as much electricity as the battery at a given weight, also having a long life. Compared with the battery, the hyper capacitor is much faster and easier to charge, being safer in use, showing much lower resistance, and providing an excellent low-temperature charge and discharge performance. However, the hyper capacitor has high self-discharge, low cell energy and a linear discharge voltage, which prevent it from using the full energy spectrum. Due to these disadvantages, the hyper capacitor fails to take a main position in the market.
Therefore the lithium-based batteries still dominate the market and such a situation will continue for a long time. However, the lithium-based batteries also face some challenges. They are not as robust as some other rechargeable technologies. They require protection from being over charged and discharged too far. Also, they are sensitive to temperature and misuses of voltage and current. If proper conditions are not satisfied, their life will degrade easily.
Besides, aging process occurring in the lithium-based batteries is another problem. It is dependent upon not only time or calendar but also the number of charge/discharge cycle that the batteries have undergone. What is more, they are potentially explosive and can set fire if not under proper protection.
To solve these issues, battery management engineers have paid great efforts. They come up with battery models and empirical studies have been conducted to try to secure and increase the reliability of lithium use. From these models and studies, engineers have been developing algorithms and hardware to handle the battery security, user safety and battery operational condition. The battery management system (BMS) and lots of literatures produced from the studies define them in details, with various sets of functions.
Over the years, BMS performances have increased significantly, bringing the lithium-based battery technology to the masses. And still, BMS based new models from new empirical studies are being developed.